The second and all steel finished production prototype of the post war prototypes. Very similar to GX2501-2. It was also made in 1951 and built on the same .380 platform, but this one has sights and a barrel. It also has the new post war finish and was presumably test fired.
Note Magazine has been cut and modified in the middle for what is presumed to lengthen it. It also bears the number "GX-397"
The factory letter states the pistol was an experimental prototype pistol kept by the colt factory.